This invention relates generally to door locks, and, in particular, to door-mounted high-security locking mechanism.
The desire for high security, auxiliary door locks has been recognized for decades, and many patents have issued which concern this subject matter. Door-mounted devices may be broadly classified in terms of where they attach to the inside of the door. That is, there are some devices which provide support under the door knob, others which mount near the floor, and still others which mount elsewhere on the door below the level of the door knob.
In terms of door knob-coupled arrangements, a search of the prior identified the following U.S. Pat. Nos.:
U.S. Pat. No. 790,653xe2x80x94an elongated door securer is locked into place through user engagement of an articulating joint;
U.S. Pat. No. 3,583,743xe2x80x94includes a ratchet mechanism enabling the user to more quickly spread the length of the bar between the door knob and the floor;
U.S. Pat. No. 4,070,049xe2x80x94features a telescoping brace which fits between an inside face of the door and an adjacent support surface such as a wall;
U.S. Pat. No. 4,300,796xe2x80x94uses a pin on a chain which engages with indents on a telescoping security bar to adjust the length thereof;
U.S. Pat. No. 4,438,640xe2x80x94includes an adjustable prop member which fits between a door knob and the floor, but which optionally includes lock and/or warning means to further help guard against unauthorized entry;
U.S. Pat. No. 4,822,086xe2x80x94an adjustable-length member telescopes between a floor and mounts to a point on the door immediately below a door knob;
U.S. Pat. No. 5,064,232xe2x80x94an adjustable security bar with one end with a pivot mount against the floor, and another end with a cup-shaped recess that fits over round knobs;
U.S. Pat. No. 5,392,026xe2x80x94an elongate member which fits between a door knob and a floor, includes an alarm device which triggers in response to physical tampering above a given threshold level;
U.S. Pat. No. 5,544,386xe2x80x94a door stopper device having an upper U-shaped end which couples to a door knob, and a plurality of feet which rest against the floor and the bottom edge of the door itself; and
U.S. Pat. No. 5,988,710xe2x80x94a variable length security bar which permits telescoping adjustment of proximal and distal sections.
In terms of mechanisms which attach lower to the floor, the following U.S. patents were identified:
U.S. Pat. No. 1,332,473xe2x80x94an auxiliary door lock which fastens to the bottom edge of the door toward the side edge of the door which opens, having a plate 6 which is urged downwardly against the floor through a turnbuckle arrangement.
U.S. Pat. No. 2,709,615xe2x80x94a spring-loaded door stop engages with the bottom edge of a door, to stop the door from swinging in either direction
U.S. Pat. No. 4,641,869xe2x80x94a door brace includes an elongate canted arm having an upper end which interlocks with the door, and a lower, floor-engaging end spaced away from the door. The upper end is shaped and dimensioned such that when forced entry is attempted, the door is compressed into interlocking engagement with the upper end of the arm, enabling the brace to resist shear forces which tend to separate the upper end of the brace from the door during an attempted forced entry.
U.S. Pat. No. 5,135,273xe2x80x94a door prop mounted just above the bottom edge of the door claims to be easy to install, while allowing the door to be opened a small amount while remaining insufficient for entry. A ratchet with saw teeth is used for adjustment purposes.;
U.S. Pat. No. 5,217,268xe2x80x94a variation of the mechanism disclosed in U.S. Pat. No. 5,135,273, naming the same individual as inventor;
U.S. Pat. No. 5,218,341xe2x80x94a door locking device with an adjustable shaft having an arcuate shape, which extends between the floor and a point on the inside of the door. An alarm device is mounted on the shaft portion which is responsive to shocks affecting the door handle above a predetermined threshold value.
The subject invention improves upon the art of high-security auxiliary door locking devices by providing a brace having an upper section which pivotally attaches to the inside of a door, and a lower section which engages with the floor at a distance spaced apart from the door. In contrast to existing devices, the lower section includes a pair of floor engaging ends, and the upper section preferably pivotally attaches at one or more points above the level of the door knob. Although a single pivotal attachment may be used, in the preferred embodiment, a transverse bar is used across the back of the door, which hinges at two points near the side edges of the door. With such an arrangement, application of an entry force to the outside surface of the door, causes the door to move upwardly against the jam for additional resistance.
In a basic configuration, the security brace according to the invention may be used by an individual within a home or a room and flipped up or otherwise adjusted so as not to interfere with door opening for ingress and egress. In an alternative embodiment, however, to obtain entry from outside, a small lockable high-security door is provided, enabling an individual with a key to unlock the door, reach in, and pull up on the brace to gain entry. Preferably a chain is provided for such purpose. To enhance aesthetic appeal, a brace according to the invention may be embedded within the door itself, with outer coverings and surfaces being used to obscure the structure when not in use.